(1) Technical Field
This invention relates to grapples or grapnels for use in the recovery of submarine communication cables from the ocean floor. The grapple attached to a towing vessel by cable is dragged along the ocean bottom across a known path of a submarine cable in order to ensnare, raise the cable to the surface and aboard the towing vessel intact or in part, for purposes of repair and maintenance.
Tension registering apparatus presently in use aboard tow vessels indicate changes in tension pressure of the Cable Catch, Clamp and Cut (CCC&C) grapple under tow if and when the cable is ensnared. When a particular pressure is registered the tow vessel is stopped and maneuvered in such a way as to enable it to haul up the submarine cable intact or in part if the grapple is equipped with a cutting capability.
(2) Background Art
Very often after many failures at recovery with the resultant loss of time and expenditure, the more complex grapple (grapnels) presently in use have been set aside and it has been necessary to revert to the old hook drag type grapnel in order to retrieve the cable.
The advanced grapnels presently in use (Note: References) offer no variable penetration of their ploughshares (scoops) into the sea bottom. As a result the grapnel often passes over a buried cable or the reverse occurs where the fixed ploughshare digs unnecessarily into the ocean floor causing premature and misleading tension readings on the tow vessel resulting in a loss of time at the very least.
My grapple is designed to be dragged on and parallel to the ocean floor with little or no penetration on soft or rock hard bottoms. It does however incorporate an interchangeable penetration (insert) device at the nose of each scoop. A "scoop insert" can be used to provide zero penetration on rock hard bottoms to maximum penetration for sand, soft silt and muddy bottoms. Cable recovery even with a variety of ocean bottom conditions is made more highly probably with my invention.
Rocks or other debris often clog present grapnels preventing ensnarement of a cable when its path is crossed or they prematurely actuate the clamping and/or cutting mechanisms.
The scoops of my invention are so designed as to allow rocks to pass through with little change of anything else being guided up and into the clamping mechanism other than a submarine cable. Only a cable firmly and properly placed (guided by scoop design and the forward motion of the CCC&C) will actuate the clamping mechanism of my invention.
Time and effort is now lost as a result of misleading tension readings caused by grapples catching onto rocks or other submerged objects.
My invention immediately indicates by electronic/radio signal when a cable is securely held and clamped. It will also indicate by signal if and when the cable is cut. This combination of signal and/or signals in conjunction with tension readings on the tow vessel will more accurately reflect the grapnel's disposition on the ocean bottom and allow for proper maneuvering responses by the towing vessel.
Some grapples now in use only ensnare the cable and using its own (cable) weight and tension to cut it as it is raised toward the surface. It is then necessary to replace this with a different form of grapple, drag once again to relocate the cut cable, and snare and raise it to the surface.
With my invention the cable is caught and clamped. It may then be cut and the desired side brought to the surface.
Some grapples now in use after ensnaring, have caused distortion and serious damage to the cable. Often after the cable is ensnared and while it is being raised to the surface it breaks as a result of the distortion which has seriously weakened it, although it was meant to be recovered intact.
Often after a cable is ensnared and is meant to be cut and raised, the cutting device does not work because of clogging rocks or a distorted cable.
With my invention the cable is not damaged or distorted. Once clamped (electronically signalled) and without distortion it can be safely raised to the surface intact. If it is desired to cut one side of the cable (pre-set aboard the tow vessel) and raise the clamped side, there is little that can hinder the proper operation of the cutting mechanism.
All of the above problems were recently visibly observed by the writer aboard an ocean-going cable (tow) vessel. Often many hours, days and even weeks were wasted in futile efforts to ensnare one (cut or uncut) submarine communication cable using the very latest state-of-the art grapple devices.